The present invention relates to a computer based grading system of gems, including the method of construction of a database serving the said system. The method is particularly useful for communication of grading results over the phone or Web, when the parties discussing the results rely on the image of the target gem as displayed by the system.
A major problem facing the gem dealer, grader and jeweler is how to accurately assess and grade consistently the color of a given gem, what descriptive language to use and how to communicate the color of gems over the fast and growing Internet or, for that matter, over the phone.
The color gamut of gems is vast, including thousands of color possibilities. Using the present methods for color communication used today, which are briefly described below, one finds it difficult or practically impossible to communicate and describe the accurate color (hue, saturation and tone) of a certain gem.
Sending the actual images of a large number of gems is time consuming due to the limitations of the speed of transfer of data. Even if such a transfer would be faster in the future one is still left with the problem of grading the gems according to accepted grades of colors, which are well defined and known.
Existing systems for color grading of gems, are for example:
The Gemset (GIA Gem Instrument, the Gemological Institute of America, Carlsbad, Calif.). This is a method of determining the color grade of gems by comparing the color of a gem to be graded, with plastic molds representing round shapes of various hues, tones and saturations. Each sample is labeled with the GIA nomenclature. The Gemset has several drawbacks:
1. Comparing real gems to plastic samples is difficult due to the different look, texture, brilliance and sparkle of plastic and real gems.
2. The presence of only rounds samples may affect the quality of grading when comparing them to gems of other shapes.
3. Limited amount of samples of colors, (324) as not all colors are present.
4. Some colors have to be interpolated or estimated by the grader or examiner, (tone and saturation) causing inconsistency of the results, especially when the same gem is examined by several experts.
5. Difficulty to find the right sample to compare with the real gem.
6. The fading of the colors of the plastic samples after a while.
7. No record of the gem grading is left after the process.
8. One can communicate the results of the grade over the phone or Internet, only if the receiving party a) has the Gemset b) can pick the same color sample, and c) reach the same conclusion as the examiner.
Advantages of the Gemset method: an accepted nomenclature by the trade.
The Gemdialogue: consists of flat, transparent acetate sheets having 10 zones of saturation levels (from 10% to 100%) in 44 spectral hues and an additional sheet of acetate having tone grade from black to transparent.
Draw backs are obvious, and all the above drawbacks apply. In addition to these:
a) Too much speculation is left to the grader.
b) The grades and nomenclature used to describe the color are not easy to communicate, say P2B70/30 which means moderate purplish blue, zone 70 (70% saturation) with the 30% black mask overlay.
c) One finds it difficult to visualize the color of the described gem.
The Munsell Book of Color (Macbeth div. of Kollmorgen Instruments Corp. New Windsor, N.Y.). An elaborated system used to determine colors, using 1600 flat, glossy, opaque, printed chip samples in 40 pages each representing a certain hue
Drawbacks are as above. This method is not suitable for grading gems.
The Inventor is the author of a 2-volume book related to gems, titled “The Dealers Book of Gems and Diamonds”, 1997. These books deal with gemology and commercial aspects of gems trading and processing.
The following patents, for example, cover the issue of gem evaluation, grading and reporting, but none covers the invention henceforth described: U.S. Pat. Nos. 5,899,503; 4,291,975; 6,239,867; 5,966,673; 5,615,005; 4,534,644; 4,527,895; 4,461,568.
Other patents cover the field of color selection, for example: U.S. Pat. No. 5,103,407 (Gabor). Color selection methods are practiced by computer methods running on color screens, for example: the color selection method offered by Microsoft Windows for non-standard colors available for their “desk top” opening screen.